How to use the GridView component

The GridView class renders a table of data from a data collection. Each item in the data provider is displayed as a row, divided into columns for the item's fields. Grid views support selecting a row, scrolling, and custom cell renderers for each column.

Live preview of the GridView component

The Basics

Start by creating a GridView control, and add it to the display list.

var gridView = new GridView();
addChild(gridView);

Data provider and columns

To render some data in the grid view, pass in a collection that contains an object for each row.

gridView.dataProvider = new ArrayCollection([
    { item: "Chicken breast", dept: "Meat", price: "5.90" },
    { item: "Bacon", dept: "Meat", price: "4.49" },
    { item: "2% Milk", dept: "Dairy", price: "2.49" },
    { item: "Butter", dept: "Dairy", price: "4.69" },
    { item: "Lettuce", dept: "Produce", price: "1.29" },
    { item: "Broccoli", dept: "Produce", price: "2.99" },
    { item: "Whole Wheat Bread", dept: "Bakery", price: "2.49" },
    { item: "English Muffins", dept: "Bakery", price: "2.99" }
]);

Next, define the columns in the grid view, so that it knows which fields from the data provider's items to display. One of the items from the data provider appears below.

{ item: "Broccoli", dept: "Produce", price: "2.99" },

The item has three fields, item, dept, and price. Create a separate GridViewColumn for each of the fields in the item, and pass them to the columns property.

gridView.columns = new ArrayCollection([
    new GridViewColumn("Item", (data) -> data.item),
    new GridViewColumn("Department", (data) -> data.dept),
    new GridViewColumn("Unit Price", (data) -> data.price)
]);

The first parameter of the GridViewColumn is the text to display in each column header. The second parameter is passed to the itemToText() property, which is a function that returns the text to display in a cell renderer.

Items in the collection are not required to be anonymous structures, like { item: "Bacon", dept: "Meat", price: "4.49" } in the example above. Class instances are allowed too (and encouraged as a best practice; you should prefer classes over anonymous structures).

Selection

Add an event listener for Event.CHANGE to perform an action when the user selects a different item.

gridView.addEventListener(Event.CHANGE, gridView_changeHandler);

Check for the new value of the selectedItem property in the listener.

function gridView_changeHandler(event:Event):Void {
    var gridView = cast(event.currentTarget, GridView);
    trace("GridView selectedItem change: " + gridView.selectedItem.item);
}

Alternatively, the value of the selectedIndex property references the index of the rows in the grid view's collection, in the order that they were added.

function gridView_changeHandler(event:Event):Void {
    var gridView = cast(event.currentTarget, GridView);
    trace("GridView selectedIndex change: " + gridView.selectedIndex);
}

Add or remove rows

To add a new row at the end, pass an object to the data provider's add() method.

var newRow = { item: "Gala Apple", dept: "Produce", price: "1.00" };
gridView.dataProvider.add(newRow);

To add a new row at a specific position, pass an object to the data provider's addAt() method.

var newRow = { item: "Banana", dept: "Produce", price: "0.32" };
gridView.dataProvider.addAt(newRow, 0);

In the example above, a new row is added to the beginning.

Similarly, to remove a row, call remove() or removeAt() on the collection.

gridView.dataProvider.removeAt(0);

Cell renderers

A cell renderer is a Feathers UI component that displays one of the fields from a single row displayed in a GridView or TreeGridView component. In other words, a GridView typically contains many cell renderers in a two-dimensional grid — with each one rendering a different field from each row in the collection.

Feathers UI provides a default ItemRenderer class, which can display data in many different ways that cover a variety of common use-cases. However, components like GridView also support custom cell renderers, which allow developers to render the grid view's data in infinite unique ways.

Consider a collection of items with the following format.

{ item: "Gala Apple", dept: "Frozen", price: "3.99", icon: "https://example.com/img/pizza.png" }

While the default ItemRenderer class can easily display some text and an image, creating a custom cell renderer for this simple data will be a good learning exercise.

A custom cell renderer designed to display this data might use a Label to display one of the strings, and an AssetLoader to display the image. The following example creates a DisplayObjectRecycler which instantiates these components and adds them to a LayoutGroupItemRenderer — a special base class for custom cell renderers.

var recycler = DisplayObjectRecycler.withFunction(() -> {
    var cellRenderer = new LayoutGroupItemRenderer();

    var layout = new HorizontalLayout();
    layout.gap = 6.0;
    layout.paddingTop = 4.0;
    layout.paddingBottom = 4.0;
    layout.paddingLeft = 6.0;
    layout.paddingRight = 6.0;
    cellRenderer.layout = layout;

    var icon = new AssetLoader();
    icon.name = "loader";
    cellRenderer.addChild(icon);

    var label = new Label();
    label.name = "label";
    cellRenderer.addChild(label);

    return cellRenderer;
});

Developers are not required to use the LayoutGroupItemRenderer class. In fact, a custom cell renderer may be created from any OpenFL display object, including primitives like openfl.display.Sprite and all other Feathers UI components.

Both GridView and GridViewColumn define cellRendererRecycler properties. On GridViewColumn, the cellRendererRecycler property may be used to customize the cell renderers in that specific column. On GridView, the cellRendererRecycler property may be used to customize the default cell renderers used when a particular column doesn't have a specific cell renderer.

var column = new GridViewColumn("Item", (data) -> data.item);
column.cellRendererRecycler = recycler;

So far, the DisplayObjectRecycler creates the cell renderer, but it doesn't understand how to interpret the data yet. A custom update() method on the recycler can do that.

recycler.update = (cellRenderer:LayoutGroupItemRenderer, state:GridViewCellState) -> {
    var label = cast(cellRenderer.getChildByName("label"), Label);
    var loader = cast(cellRenderer.getChildByName("loader"), AssetLoader);

    label.text = state.text;
    loader.source = state.data.icon;
};

When the update() method is called, it receives the cell renderer and an GridViewCellState object. GridViewCellState has a number of useful properties.

In this case, the value of text is displayed by the Label, and the icon field from data (remember the example row from above, with item and icon fields) is displayed by the AssetLoader.

It's always a good practice to provide a reset() method to the DisplayObjectRecycler, which will clean up a custom cell renderer when it is no longer used by the GridView.

recycler.reset = (cellRenderer:LayoutGroupItemRenderer, state:GridViewCellState) -> {
    var label = cast(cellRenderer.getChildByName("label"), Label);
    var loader = cast(cellRenderer.getChildByName("loader"), AssetLoader);

    label.text = "";
    loader.source = null;
};

Warning: A DisplayObjectRecycler without a reset() method could potentially cause memory leaks or other unexpected behavior, if the same data needs to be used again later.

Resize and sort columns

Set the resizableColumns property to true on a GridView to allow users to drag the dividers between columns to resize them.

gridView.resizableColumns = true;

Set the sortableColumns property to true to allow users to click a column header to sort the items in a GridView.

gridView.sortableColumns = true;

To programmatically adjust the sorting, set the sortedColumn property and the sortOrder property.

gridView.sortedColumn = gridView.columns.get(0);
gridView.sortOrder = ASCENDING;

Styles

A number of styles may be customized on a GridView component, including an optional background skin and the appearance of the grid view's scroll bars.

Background skin

Optionally give the grid view a background using the backgroundSkin property. The following example sets it to a RectangleSkin instance.

var skin = new RectangleSkin();
skin.border = SolidColor(1.0, 0x999999);
skin.fill = SolidColor(0xcccccc);
skin.width = 16.0;
skin.height = 16.0;
gridView.backgroundSkin = skin;

The border and fill properties of the RectangleSkin are used to adjust its appearance. They support a variety of values — from solid colors to gradients to bitmaps.

The grid view automatically calculates its preferred size based on the initial dimensions of its background skin (accounting for some other factors too, like the layout and scroll bars), so it's important to set a skin's width and height properties to appropriate values to use in this calculation.

See Skinning with common shapes for more details about how to use RectangleSkin with the LineStyle and FillStyle enums that change its border and fill appearance.

The appearance of the grid view's border or fill may be customized to change when the grid view is disabled. In the next example, setting the skin's disabledFill method makes it switch to a different fill when the grid view is disabled.

skin.disabledFill = SolidColor(0xffcccc);

Similarly, use the skin's disabledBorder property to change the border when disabled.

skin.disabledBorder = SolidColor(2.0, 0x999999);

In the examples above, the grid view uses the same RectangleSkin for all states, and that skin listens for changes to the grid view's current state. Alternatively, the grid view's disabledBackgroundSkin method allows the grid view to display a completely different display object when it is disabled.

var defaultSkin = new RectangleSkin();
// ... set border, fill, width, and height
gridView.backgroundSkin = defaultSkin;

var disabledSkin = new RectangleSkin();
// ... set border, fill, width, and height
gridView.disabledBackgroundSkin = disabledSkin;

In the example above, the grid view will have a separate skins when enabled and disabled.

Scroll bars

The scroll bars in a GridView component are of type HScrollBar and VScrollBar. Their appearance may be customized globally in a theme, or they may be customized outside of a theme on an specific, individual grid view.

See How to use the HScrollBar and VScrollBar components for complete details about which styles are available for the scroll bars.

Style scroll bars globally

Use the HScrollBar and VScrollBar classes in a theme to provide a function that globally styles all scroll bars in your project.

styleProvider.setStyleFunction(HScrollBar, null, setHScrollBarStyles);
styleProvider.setStyleFunction(VScrollBar, null, setVScrollBarStyles);

The functions should use the following signatures.

function setHScrollBarStyles(scrollBar:HScrollBar):Void {
    // ... set styles here
}

function setVScrollBarStyles(scrollBar:VScrollBar):Void {
    // ... set styles here
}

Style scroll bars in a specific GridView

The scrollBarXFactory and scrollBarYFactory properties may be used to customize the creation of an individual grid view's scroll bars.

gridView.scrollBarXFactory = () -> {
    var scrollBar = new HScrollBar();
    // ... set styles here
    return scrollBar;
};

gridView.scrollBarYFactory = () -> {
    var scrollBar = new VScrollBar();
    // ... set styles here
    return scrollBar;
};